Wavelength Division Multiplexing (WDM) is a technology used in the field of optical communications. Conventionally, an optical channel monitor (OCM) is used in a wavelength division multiplexing system. The optical channel monitor is used to monitor the wavelength and optical power of signals in channels for wavelength multiplexed signals. For example, a wavelength control device such as a wavelength selectable switch (WSS) controls each channel based on monitor information from the optical channel monitor. Furthermore, monitor information from the optical channel monitor may also be used for generating an alarm when the wavelength shifts. Therefore, the optical channel monitor is expected to provide very precise monitoring. The precision for wavelength monitoring is expected to be in the range of ±0.05 nm or less. Moreover, there is a system in which an optical channel monitor detects a shift in wavelengths of about ±0.1 nm and then sounds an alarm.
In the related art there is a wavelength multiplexing optical transmitter that uses an arrayed waveguide grating (AWG) and an optical filter in an output unit of a wavelength multiplexer, and includes a monitor that identifies wavelengths to monitor problems such as wavelength shifts. The wavelength multiplexing optical transmitter then sounds an alarm and blocks light outputted from an abnormal optical transmitter. Moreover, there is also a wavelength multiplexing optical transmitting system that measures input and output optical powers of an amplifying medium that amplifies wavelength multiplexed light, and then sets passing wavelength properties of a variable gain equalizer connected to a transmission path, based on data from a database that indicates wavelength properties for each type of transmission path.